Liquid-fuel burner



June 1967 o. H SCHADE, JR 3,323,574

LIQUID-FUEL BURNER Filed April 15, 1965 2 Sheets-Sheet .2

w I f /36 m2 INVENTOR.

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United States Patent 3,323,574 LIQUID-FUEL BURNER Otto H. Schade, J12,North Caldweil, NJ assignor to Radio Corporation of America, acorporation of Delaware Filed Apr. 15, 1965, Ser. No. 448,533 Claims.(Cl. 158-54) ABSTRACT OF THE DISCLOSURE the lighter vapors. Thesuperheated vapors are then directed to a burner where the vapors areburned.

This invention relate to liquid-fuel burners, and particularly to animproved and novel means for utilizing, in an efficient and trouble-freemanner, liquid fuels, such as leaded gasoline, with such burners.

In certain applications in which liquid-fuel burners are used, such asin the provision of heat for thermoelectric generators used in remoteand out-ofthe-way places, it is desirable that the burners operateunattended in an efiicient, safe, and trouble-free manner for longperiods of time. For reasons of practicality and efficiency, it is alsodesired that the burners be fireable with a Widely used and inexpensivefuel, such as leaded gasoline, andthat the burners be operable withoutpowenconsuming auxiliary devices, such as combustion-air blowers, andthe like.

For avoiding the use of auxiliary combustion-air blowers, a vaporizingburner which aspirates its own combus- .tion air is preferable in theseappliactions. One problem with known vaporizing liquid-fuel burners isthe difliculty of obtaining complete combustion of the fuel entering thecombustion zone. Gasoline and related petroleum fuels compriseconstituents having boiling points which vary over a relatively widerange, and it frequently occurs that the liquid fuel is incompletelyvaporized prior to its introduction into the burner combustion zone. Theunvaporized constituents do not completely burn thereby producing sootwhich accumulates on the various burner members and upon the element orload heated by the burner. The soot deposits interfere with eflicientcombustion of the fuel and with eflicient and uniform transfer of heatto the burner load.

A further problem with the use of liquid-fuels, and especially leadedgasoline, is that various substances from the fuel are deposited ontothe walls of the various passageways leading to and Within the burnerwhich constrict and eventially clog these passageways. Also, certain ofthese deposits are combustible thereby creating a fire hazard. Frequentcleaning of these passageways is thus required.

It is an object of this invention to provide a novel and improvedliquid-fuel vaporizing burner operable safely and efliciently for longperiods of unattended time, and usable with liquid fuels such as leadedgasoline.

Another object is to provide a novel and improved means for convertingliquid fuels such as leaded gasoline into a vapor suitable for efficientand trouble-free use wit-h burners.

For achieving these objects, a vaporizer is provided to which the liquidfuel is fed under pressure. Within the vaporizer, and in the path of theliquid fuel, is a first region in which the liquid fuel is heated to apreselected temperature for vaporizing a preselected portion of thelower boiling point constituents of the fuel. The heated fuel is thenpassed into a separating chamber wherein the non-vaporized constituentsare separated from the vaporized constituents. Within the separatingchamber, the nonvaporized constituents may be further heated forvaporizing any of the lower boiling point constituents entrainedtherewith. The vaporized fuel flows from the separating chamber into asecond region where the vapor is superheated and wherein any liquiddroplets traveling with the vapor are vaporized. The superheated vapors,virtually devoid of liquid droplets, then pass into a burner wherein thevapors are burned.

The burner may comprise a presently known burner. However, preferablythe burner is designed to provide a controlled flame-front, wherein thedeposition onto portions of the burner of certain salts normally formedin the combustion zone of the burner is avoided.

This and other features of the vaporizer and burner are described ingreater detail hereinafter in connection with a description ofembodiments illustrated in the drawings, wherein:

FIG. 1 is a side elevation in section of one embodiment of a vaporizer,

FIG. 2 is a side elevation in section of another embodiment of avaporizer, and

FIG. 3 is a side elevation, partly broken away and partly in section, ofa liquid'fuel vaporizing burner and a thermoelectric converter loadheated by the burner.

The vaporizer it} shown in FIG. 1 comprises a body casing 12 including apassageway 14 coupled to a pipeline 15 leading from a source of liquidfuel 17. For applications in remote areas it is highly advantageou thatthe liquid-burner be operable with fuels normally provided for otherpurposes, thereby simplifying transport and storage problems. To thisend, it is desirable that the liquidfuel burners be operable withcommercially available automotive gasoline, and especially leadedgasoline.

Passageway 14 opens into the lower end of a vertical and centrallydisposed open-ended, tubular member 16 having a number, e.g., 4,longitudinally extending bores 13 therethrough. Mounted on member 16 andextending over the open ends of bores 18 is a deflector 20 having anannular downwardly extending flange 22.

Member 16 provides a first vaporizingregion 18' wherein most of theliquid fuel is vaporized, and to this end, member 16 is heated. This isaccomplished by heating an extending portion 24 of casing 12,. the heatreceived by portion 24 passing by conduction upwardly through casing 12to member 16 which is firmly secured within an annular flange 26 ofcasing 12, as by means of a screw thread, not shown. Casing portion 24may be heated by the exhaust gases from the burner fired by the fuelfrom the vaporizer, using known heat transferring means, not shown. Theliquid fuel, such as gasoline, is fed into the casing passageway 14 at agiven rate and at pressures of around 525 p.s.i.g. by known pump means(not shown), and the casing portion 2a is heated at a rate suflicient tomaintain the lower end of tubing 16 at a temperature (when gasoline isused) of around 160 C.

Gasoline comprises numerous hydrocarbon constituents having boilingpoint temperatures ranging from around 40 C. to C. Within the firstvaporizing region 18 substantially all of the hydrocarbon constituentsof the gasoline are vaporized in the nucleate boiling mode. The higherboiling-point hydrocarbon constituents, that is, heavy-ends of thegasoline, are not vaporized but remain in the liquid state. In general,satisfactory results m) are achieved if the vaporizer is operated tovaporize about 90-95% of the gasoline (by volume) fed to the vaporizer.The unvaporized 10% of the fuel comprises, in general, the gasolineconstituents having boiling points above 160 C. If leaded gasoline isused, it is found that the heavy-ends or high-boiling point constituentsof the gasoline include some of the tetraethyl lead additive.

After being heated in the first vaporizing region 18', the mixture ofvapor and heavy-ends liquid droplets is directed downwardly by deflector20 into the upper portion of a separating or settling chamber having avolume relatively large in comparison with the volume of the firstvaporizing region 18. Settling chamber 30 comprises an outer wall 32mounted on a flange 34 of casing 12, the upper surface of casing 12serving as the bottom of chamber 30, and the top end of chamber 30 beingclosed by a superheating member 40, described hereinafter.

Due to the comparatively large volume of the settling chamber 30, theliquid droplets-vapor mixture has a low velocity, thereby allowin theheavy-ends liquid droplets to separate from the vapor and settle to thebottom of chamber 30. Casing 12 is heated, as described, and the pool ofheavy-ends collected in the lower portion of settling chamber 30 isfurther heated, whereby any lower boiling point constituents of theliquid fuel entrained with the heavy-ends are boiled out of theheavy-ends pool.

Opening into the settling chamber 30 near its lower end is a feed tube44 which extends through casing 12 and into a discharge or float chamber46 mounted on casing 12 and having a known type float valve systemtherein. The heavy-ends drain through the feed tube 44 and into thefloat chamber 46 where, when suflicient heavy ends accumulate to liftthe float and open the valve, the heavy ends are discarded through adrain tube 48. Float chamber 46 is vented by means of a tubing 50 toprovide A pressure equalization between the chamber 46 and settlingchamber 30.

To prevent condensation of the fuel vapors which pass into and out ofthe float chamber 46 through tubing 50, float chamber 46 is alsomaintained at an elevated temperature. This may be accomplished bymaking the wall of float chamber 46 of a good thermal conductivitymaterial and heat insulating the chamber (by known means, not shown) toprevent heat loss therefrom whereby the Wall conductivity and thecirculating hot vapors serve to heat the chamber to a sufficiently hightemperature.

superheating member has a vapor inlet 62 dis-posed above the deflector20 which leads to a passageway 64 extending through member 40 to a spud66 having a relatively small diameter orifice 68. The vapors in settlingchamber 30, mostly free of heavy-ends droplets, pass around and upwardlyof deflector 20 and into pass-ageway 64 through inlet 62.

Passageway 64 comprises the second vaporizing or superheating region,and to this end, member 40 is heated. An extending portion '70 ofsuperheating member 40 is heated, preferably also by the hot exhaustgases from the burner, and the heat passes by conduction throughoutmember 40. In one embodiment, and wherein gasoline is used as the fuel,the operating temperature of superheating member 40 in the immediateregion of vapor inlet 62 is around 220-230 C. and decreases to about190-200" C. at the orifice end of member 40. Within the passageway 64,the vapors are superheated to a temperature higher than the boilingpoint of the highest boiling point constituents of the raw fuel. Thisinsures that the vapors, which may include small amounts of heavy-endsliquid droplets entrained with the vaporized lighter ends, are virtuallydevoid of liquid droplets as the vapors approach and pass outwardlythrough orifice 68.

The vapors are then fed to an injector, such as the one shown in FIG. 3,described hereinafter, where the vapors are mixed with air, fed to aburner, and immediately burned.

Casing 12, the first vaporizing member 16, deflector 20, and thesuperheating member 40 are preferably made of high thermal conductivitymaterials having a high resistance to oxidation and chemical attack.Aluminum alloys low in copper content have proven to be satisfactory.Aluminum is suitable for the wall of the settling chamber, and brass andstainless steel are suitable for the float chamber 46. The orifice spud66 is preferably made of a free-machining aluminum alloy.

The use of Vaporizers as described above avoids many of the problemsassociated with the use of prior-art liquidfuel burners. Thus, forexample, by removing the heavy ends, complete vaporization of the vaporsfed to the burner and complete combustion of the fuel-air mixture andavoidance of soot are obtained.

Further, a major detriment to long and unattended operation ofliquid-fuel burners is the clogging of small passages and jet orificesby various deposits. One of the main causes of such clogging is thepresence of liquid droplets in the vapors stream. It appears that themetal walls of the pipelines act as a catalyst and that the liquiddroplets go through chemical reactions which produce various deposits asthe end products of the reactions. Use of the present vaporizer greatlyreduces such clogging by providing almost complete vaporization of theliquid fuel. This is accomplished, as described, by first removing thediflicult-to-vaporize heavy-end hydrocarbon constituents of the liquidfuel and thereafter superheating the vapor to insure that anyliquid-fuel droplets are completely vaporized. In one test of theembodiment shown in FIG. 1, for example, and using a leaded gasolinefuel, the vaporizer was operated in excess of 100 hours in daily 8-hourcycles without the formation of deposits along the pipeline walls and atthe orifice 68. In contrast, after as little as five hours of use withknown Vaporizers, deposits accumulated at the discharge orifice of thevaporizer which nitieeably impeded the vapor flow from the vaporizer.

It is also found that with known Vaporizers the heaviest fuel-ends, evenif vaporized, settle out as a heavy liquid in the pipelines leading tothe burner and constitute a fire hazard. Removal of these heavy-fuelends as herein described avoids this problem. Further, removal of atleast some of the tetraethyl-lead additive of leaded gasoline, if used,reduces the formation of salt deposits in the fuel passagewaysimmediately adjacent to the burner combustion zone. Such salts areformed in the flame-front zone during the combustion of the gasolinevapors and tend to condense on and clog the passageways through theMeker-type gridworks normally used in vaporizing-type burners.

The vaporizer 30 shown in FIG. 2 comprises an inverted cup-shaped member82 haivng an outer or side wall 84 closed by a heat receiving andconducting end member 36. Outer wall 84 includes an upper thin wallsection 83 and an intermediate thick wall section having a plurality,e.g., l2, longitudinally extending bores 92 therein, the bores beingarranged in a circular array coaxial with member 82. The lower end ofthe bores open into an annular chamber 94 communicating with a coupling96 through which a liquid fuel is admitted. The upper ends of the bores92 are open but have a annular deflector 100 extending thereover fromoutside wall 84. Received coaxially within tubular member 82 is anelongated inner tubing 102 having a passageway 104 therethrough and acoaxial intermediate cylindrical mem ber 106 disposed around tubing 102.Tubing 102 is spaced from outer wall 34. The lower end of cylindricalmember 106 extends below the thick wall section 90 and provides, with anannular member 108 and the lower end 110 of outer wall 84, a floatchamber 112. Float chamber 112 is coaxial with tubing 102. The means forassembling and sealing the various vaporizer parts with respect to oneanother are neither shown nor described since such means will beapparent to those skilled in the art.

Cit

The vaporizer 80, for convenience of illustration, is shown as anintegral member.

The liquid fuel is admitted under pressure through coupling 96 into theannular chamber 94 and into the bores 92. The thick wall section 90 isheated by means described hereinafter and the bores 92 provide a firstvaporizing region wherein the liquid fuel is heated to a temperaturesuflicient to vaporize (when gasoline is used) about 90-95%, by volume,of the lower boiling point constituents of the fuel.

The annular space provided by the cylindrical member 106 and the insidewall of the thickened wall section 90 serves as an open-ended separatingchamber 114. The chamber 114 connects with bores 92 at its upper end andwith the float chamber 112 at its lower end.

Annular deflector 100 has a downwardly extending flange 116 whereby theheated fuel rising upwardly through the bores 92 is deflected bydeflector 100 downwardly through the open upper end of separatingchamber 114. The volume of the-separating chamber 114 is somewhat largerthan the combined volume of the first vaporizing bores92 so that thevelocity of the heated fuel in the separating chamber is suflicientlyslow to permit gravity separation of the unvaporized heavy endsconstituents from the vaporized lighter ends constituents of the fuel.The separated heavy ends pass downwardly through a passageway 118between cylindrical member 106 and the lower portion of thickened wallsection 90 and into the float chamber 112.

Float chamber 112 contains an annular hollow float 120 which cooperateswith a known spring-loaded pin valve 122 for opening and closing anorifice in an outlet coupling 124. When sufiicient heavy-ends accumulatein the float chamber to raise the float 120 a suflicient amount, valve122 is opened thereby permitting discharge of the heavyends throughcoupling 124.

The vaporized constituents of the fuel pass upwardly and outwardly ofthe settling chamber 114 through the central opening in .the annulardeflector 100 into a chamber 126 formed above deflector 100 and into thepassageway 104- extending through tubing 102. Within tubing 102 the gasvapors are superheated to a temperature higher than the highest boilingpoint constituents of the fuel and then discharged as a jet through anorifice 123 in the lower end of the tubing 102.

For heating vaporizer 80, hot exhaust gases from the burner fired fromthe vaporizer are used, as described hereinafter, to heat the upwardlyextending end member 86 of the vaporizer. The heat transferred to member86 is then conducted throughout the vaporizer for heating the firstvaporizing region (bores 92 within the thick wall section 90), thesuperheating tubing 102, and the float chamber 112. The superheatingtubing 102 is heated to a temperature higher than the temperatures ofthe first vaporizing region and float chamber, and to this end, tubing102 is secured .to the heatreceiving member 86 by means of a largecross-sectional area pedestal 132, whereby only a relatively smalltemperature drop occurs between heat receiving member 86 and tubing 102.Conversely, the thin wall section88 causes a somewhat larger temperaturedrop between the heat receiving member 86 and the thick wall section 90.Float chamber 112 is heated by conduction of heat through the outer wall82. Heating of the float chamber 112 prevents condensation of the gasvapors passing in and out of the float chamber through passageway 118.

As shown in FIG. 3, the superheated gas vapors are discharged from thelower end of tubing 102 into an injector 134 of a burner 136. Theinjector shown is of the compound Venturi type and is generally known inthe art. Air passes downwardly through the open end 138 of the Venturiand is entrained and mixed with the fuel vapors injected therein byvaporizer 80. An air regulating shutter 140 is provided for controllingthe amount of air mixed with the fuel vapors. The fuel vapor-air mixturepasses through the Venturi, past baflies 142 which provide a laminarflow of the fuel, and into the burner head 143 which includes aMeker-type gridwork 14 1. As the fuel mixture passes outwardly of theMeker gridwork 144 it is burned, the gridwork 144 preventing flashbackof theburner flame, as known. The burner flame is used 'to heat anenclosing cylindrical element 146, such as a thermoelectric converter(the details of which are not shown), and the hot exhaust gases from theburner are directed into a duct 148 leading to a known type heatexchanger, not shown, for heating the heat receiving and conductingmember 86 of the vaporizer 80.

A problem associated with the use of leaded gasoline is that lead salts,such as sulfates and oxides, are formed during the combustion of thegasoline vapors which .tend to deposit on and clog the Meker gridworkports. The Meker gridwork is so designed, and the flow of fuel to thegridwork so regulated, that deposit of these salts onto the gridwork islargely avoided. This is ,accomplished by designing the gridwork toprovide, at a stoichiometric fuel-air mixture and normal firing rate, amixture velocity-gradient in the gridwork which provides a liftedflame-front anchored only at its extremities. That is, except at theperimeter of the burner head gridwork, combustion of the fuel does notbegin. immediately adjacent the gridwork port ends, but at a smalldistance above the gridwork. In FIG. 3 the combustion zone of the fuelis indicated by the region 150. Under these conditions of combustion,the lead salts, which normallyform in the lower portion of thecombustion zone, are not deposited in the gridwork ports, but arevolatilized and carried away by the exhaust products.

Design information enabling one to design a burner for operation withliftedflame-fronts is presented in Combustion Flames and Explosions ofGases, by B. Lewis and G. Von Elbe, Academic Press, 1951, pp. 226-308.

In one embodiment, the burner head 143 has a diameter of 2 inches, andthe gridwork is formed of .008 inch slotted metal strips to provide 2.%-inch thick gridwork having ports .052 x .052 inch.

The fuel flow is about 1 lb./hr. and the center of the flame-front (onaxis) is lifted about 1 inch or more from the top of the gridwork.

What is claimed is:

1. A vaporizing burner for a liquid fuel having different boiling pointconstituents comprising:

a vertically extending member having a plurality of longitudinallyextending bores therethrough,

passage means opening into the lower ends of said bores for entry offuel therein,

means for heating said member for vaporizing a preselected portion ofthe lower boiling point constituents of said fuel,

a separating chamber having upper and lower ends and having a volumelarger than the combined volume of said bores,

means for directing the heated constituents of said fuel from said firstvaporizing bores in a downward direction into the upper end of saidseparating chamber,

a discharge chamber in communication with the lower end of saidseparating chamber,

a superheating chamber, said superheating chamber having a vapor inletin communication with the upper end of said separating chamber,

means for heating said superheating chamber for heating vapors thereinto a temperature higher than the boiling point of the highest boilingpoint constituents of the fuel,

an aspirator,

said superheating chamber opening into said aspirator for passage ofsaid superheated vapors into said aspirator, whereby said vapors aremixed with air,

7 and a burner head,

said aspirator directing said air-vapor mixture into said burner headfor consumption of said mixture.

2. A vaporizer for a liquid fuel having different boil ing pointconstituents comprising:

(a) an upstanding tubular member having therein:

(i) an array of longitudinally extending bores, the

upper ends of said bores being open,

(ii) an annular chamber having an open upper end and having a volumelarger than the combined volume of said bores,

(iii) said bores and annular chamber being in communication through theopen upper ends thereof, and

(iv) a superheating chamber communicating with said annular chamberthrough the open end thereof,

(b) a discharge chamber disposed below said annular chamber and incommunication therewith,

(c) means for heating said bores and chambers,

(d) passage means for admitting said fuel under pressure into the lowerend of said bores for vaporizing a pre-selected portion of the lowerboiling point constituents of said fuel,

7 (e) means for directing the vaporized and unvaporized portions of saidfuel downwardly through the upper end of said annular chamber, and

(f) said superheating chamber being heated to a temperature for heatingvapors therein to a temperature higher than the boiling point of thehighest boiling point constituents of said fuel.

3. A vaporizer for a liquid fuel having different boiling pointconstituents comprising:

(a) an upstanding tubular member having therein, in

coaxial and radially spaced apart relation:

(i) an outer circular array of longitudinally extending bores, the upperends of said bores being open,

(ii) an intermediate annular chamber having open ends and having avolume larger than the combined volume of said outer bores,

(iii) said outer bores and intermediate chamber being in communicationthrough the open upper ends thereof, and

(iv) an inner chamber communicating with said intermediate chamberthrough the open end thereof,

(b) an annular discharge chamber disposed below said intermediatechamber and in communication therewith,

(c) means for heating said bores and chambers,

(d) passage means for admitting said fuel under pres sure into the lowerend of said bores for vaporizing a pre-selected portion of the lowerboiling point constituents of said fuel,

(e) means for directing the vaporized and unvaporized portions of saidfuel downwardly through the upper end of said intermediate chamber, and

(f) said inner chamber being heated to a temperature for heating vaporstherein to a temperature higher than the boiling point of the highestboiling point constituents of said fuel.

4. A vaporizer for a liquid fuel having different boiling pointconstituents comprising:

an upstanding tubular member having a closed upper end, the side Wall ofsaid member including an upper thin wall section joined to the upper endof said tubular member and an intermediate thick wall section,

a plurality of longitudinally extending bores in said thick Wallsection, the upper ends of said bores being open, and passage meansopening into the lower ends of said bores for entry of fuel therein,

a tubing having a passageway therethrough extending axially of saidtubular member, said tubing being joined to the upper end of said tubingmember by a pedestal having a cross-sectional area larger than thecross-sectional area of said thin wall section,

a cylindrical member coaxial with said tubing and disposed therearoundand in spaced relation with said thick wall section,

the space between said cylindrical member and said thick wall sectiondefining an annular separating chamber having a volume larger than thecombined volume of said bores,

the lower end of said cylindrical member extending beyond the lower endof said thick wall section and being joined to said side wall forproviding an annular discharge chamber coaxial with and in communicationwith said separating chamber,

the upper end of said separating chamber being open and in communicationwith the open upper ends of said bores and with said passageway throughsaid tubing,

means for heating the upper end of said tubular member for heating, byconduction, said side wall and said tubing, said thick Wall sectionbeing heated to a temperature for volatizing a preselected portion ofthe lower boiling point constituents of said fuel in said bores, andsaid tubing being heated to a higher temperature than the boiling pointof the highest boiling point constituents of said fuel,

means for feeding said fuel into said bores, and

means for directing said vaporized and unvaporized constituents fromsaid bores downwardly through the upper end of said separating chamber.

5. A vaporizing burner for a liquid fuel having different boiling pointconstituents comprising:

a vertically extending member having a plurality of longitudinallyextending bores therethrough,

passage means extending into the lower ends of said bores for entry offuel therein,

means for heating said member,

a separating chamber in communication with the upper end of said bores,said separating chamber having a volume larger than the combined volumeof said bores,

a discharge chamber in communication with said separating chamber,

a superheating chamber in communication with said separating chamber,

means for heating said superheating chamber, and

a burner head in communication with said superheating chamber.

References Cited UNITED STATES PATENTS 665,112 1/1901 Kitson 158-54X778,577 12/1904 Hague l5853 FREDERICK L. MATTESON, 111., PrimaryExaminer.

ROBERT A. DUA, Examiner.

5. A VAPORIZING BURNER FOR A LIQUID FUEL HAVING DIFFERENT BOILING POINTCONSTITUENTS COMPRISING: A VERTICALLY EXTENDING MEMBER HAVING APLURALITY OF LONGITUDINALLY EXTENDING BORES THERETHROUGH, PASSAGE MEANSEXTENDING INTO THE LOWER ENDS OF SAID BORES FOR ENTRY OF FUEL THEREIN,MEANS FOR HEATING SAID MEMBER, A SEPARATING CHAMBER IN COMMUNICATIONWITH THE UPPER END OF SAID BORES, SAID SEPARATING CHAMBER HAVING AVOLUME LARGER THAN THE COMBINED VOLUME OF SAID BORES, A DISCHARGECHAMBER IN COMMUNICATION WITH SAID SEPARATING CHAMBER, A SUPERHEATINGCHAMBER IN COMMUNICATION WITH SAID SEPARATING CHAMBER, MEANS FOR HEATINGSAID SUPERHEATING CHAMBER, AND A BURNER HEAD IN COMMUNICATION WITH SAIDSUPERHEATING CHAMBER.